Gamma Equulei
{{Short description|Chemically peculiar A-type main sequence star in the constellation Equuleus}}
{{Starbox begin
|name = γ Equulei
}}
{{Starbox image
| image=
{{Location mark
|image=Equuleus constellation map.svg|alt=|float=center|width=240
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=γ Equ
|x=518|y=443
}}
|caption=Location of γ Equulei (circled)
}}
{{Starbox observe
|epoch = J2000
|constell = Equuleus
}}
{{Starbox character
|class = {{nowrap|A9VpSrCrEu}}
|r-i = +0.10
|variable = roAp
}}
{{Starbox astrometry
|radial_v = {{val|−16.489|0.0004}}
|parallax = 27.55
|p_error = 0.62
}}
{{Starbox detail
|mass = {{val|1.78|0.12|0.17}}
|luminosity = {{val|11.0|0.93}}
|temperature = {{val|7550|150|fmt=commas}}
|rotational_velocity = {{val|7.0|0.5}}
}}
{{Starbox catalog
| names = {{odlist | B=γ Equ | F=5 Equ | BD=+09°4732 | FK5=1555 | HD=201601 | HIP=104521 | HR=8097 | SAO=126593 }}
}}
{{Starbox reference
|Simbad = gam+Equ
}}
{{Starbox end}}
Gamma Equulei, Latinized from γ Equulei, is a double star in the northern constellation of Equuleus. It is located at a distance of around {{Convert|118|ly|pc|abbr=off|lk=on}} from Earth and is visible to the naked eye with a slightly variable apparent visual magnitude of around 4.7. The star is drifting closer to the Sun with a radial velocity of −16.5 km/s.
Properties
The primary component of γ Equulei is a chemically peculiar star with a stellar classification of {{nowrap|A9VpSrCrEu}}. It has a spectrum corresponding to an A9 main sequence star, but with unusual abundances of strontium, chromium, and europium. Stars with this type of spectral peculiarity are called Ap stars. The abundances of some metals are believed to be due to chemical stratification in the slowly-rotating star, unusual for hot main sequence stars. A fairly wide range of spectral types have been published for γ Equulei, ranging from A5 to F1, some of them also indicating unusual abundances of iron in the spectrum. γ Equulei has particularly sharp absorption lines in its spectrum, a sign of very slow rotation.
File:GammaEquLightCurve.png for Gamma Equulei, adapted from Gruberbauer et al. (2008). The red line shows the sine function which best fits the data, the period of which is 12.15 minutes.]]
γ Equulei undergoes rapid periodic variations in brightness, which places it among the rapidly oscillating Ap (roAp) stars. The apparent magnitude varies between extremes of +4.58 and +4.77. It shows pulsations in several periods near 12 minutes. The strongest pulsation is at 11.7 minutes; others are found at 11.9, 12.2, and 12.4 minutes. These are identified as a series of even and odd p-mode (pressure-induced) pulsations.
The surface magnetic field of γ Equulei undergoes slow variation, ranging from +577 G to –1,101 G. Although only 67 years of magnetic field measurements are available, a period of {{val|97.16|3.15|u=years}} has been fit to the data. This is thought to be the rotation period of γ Equulei.
γ Equulei has a magnitude 8.69 companion at an angular separation of 1.26 arcseconds.
{{clear left}}
References
{{Reflist|refs=
| last1=Gruberbauer | first1=M. | last2=Saio | first2=H. | last3=Huber | first3=D.
| last4=Kallinger | first4=T. | last5=Weiss | first5=W. W. | last6=Guenther | first6=D. B.
| last7=Kuschnig | first7=R. | last8=Matthews | first8=J. M. | last9=Moffat | first9=A. F. J.
| last10=Rucinski | first10=S. | last11=Sasselov | first11=D. | last12=Walker | first12=G. A. H.
| title=MOST photometry and modeling of the rapidly oscillating (roAp) star γ Equulei
| journal=Astronomy and Astrophysics | date=March 2008 | volume=480 | issue=1 | pages=223–232
| doi=10.1051/0004-6361:20078830 | arxiv=0801.0863 | bibcode=2008A&A...480..223G
| s2cid=54726017 | url=https://www.aanda.org/component/article?access=bibcode&bibcode=&bibcode=2008A%2526A...480..223GFUL
| access-date=16 November 2022}}
| title=Gaia Data Release 2. The catalogue of radial velocity standard stars
| last1=Soubiran | first1=C. | last2=Jasniewicz | first2=G.
| last3=Chemin | first3=L. | last4=Zurbach | first4=C.
| last5=Brouillet | first5=N. | last6=Panuzzo | first6=P.
| last7=Sartoretti | first7=P. | last8=Katz | first8=D.
| last9=Le Campion | first9=J. -F. | last10=Marchal | first10=O.
| last11=Hestroffer | first11=D. | last12=Thévenin | first12=F.
| last13=Crifo | first13=F. | last14=Udry | first14=S.
| last15=Cropper | first15=M. | last16=Seabroke | first16=G.
| last17=Viala | first17=Y. | last18=Benson | first18=K.
| last19=Blomme | first19=R. | last20=Jean-Antoine | first20=A.
| last21=Huckle | first21=H. | last22=Smith | first22=M.
| last23=Baker | first23=S. G. | last24=Damerdji | first24=Y.
| last25=Dolding | first25=C. | last26=Frémat | first26=Y.
| last27=Gosset | first27=E. | last28=Guerrier | first28=A.
| last29=Guy | first29=L. P. | last30=Haigron | first30=R.
| display-authors=1 | journal=Astronomy and Astrophysics
| volume=616 | pages=A7 | year=2018
| bibcode=2018A&A...616A...7S | arxiv=1804.09370
| doi=10.1051/0004-6361/201832795 | s2cid=52952408
}}
| title=A volume-limited survey of mCP stars within 100 pc - I. Fundamental parameters and chemical abundances
| last1=Sikora | first1=J. | last2=Wade | first2=G. A.
| last3=Power | first3=J. | last4=Neiner | first4=C.
| display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society
| volume=483 | issue=2 | pages=2300–2324 | date=February 2019
| doi=10.1093/mnras/sty3105 | doi-access=free | arxiv=1811.05633
| bibcode=2019MNRAS.483.2300S | postscript=. }}
| title=Benchmarking the fundamental parameters of Ap stars with optical long-baseline interferometric measurements
| display-authors=1 | last1=Perraut | first1=K.
| last2=Cunha | first2=M. | last3=Romanovskaya | first3=A.
| last4=Shulyak | first4=D. | last5=Ryabchikova | first5=T.
| last6=Hocdé | first6=V. | last7=Nardetto | first7=N.
| last8=Mourard | first8=D. | last9=Meilland | first9=A.
| last10=Morand | first10=F. | last11=Tallon-Bosc | first11=I.
| last12=Farrington | first12=C. | last13=Lanthermann | first13=C.
| journal=Astronomy & Astrophysics | postscript=.
| volume=642 | id=A101 | pages=13 | date=October 2020
| doi=10.1051/0004-6361/202038753 | bibcode=2020A&A...642A.101P | doi-access=free }}
| first=F. | last=van Leeuwen |date=November 2007
| title=Validation of the new Hipparcos reduction
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664
| bibcode=2007A&A...474..653V | arxiv=0708.1752
| doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
{{citation | last1=Bychkov | first1=V. D. | last2=Bychkova | first2=L. V. | last3=Madej | first3=J. | title=Secular variability of the longitudinal magnetic field of the Ap star γ Equ | journal=Monthly Notices of the Royal Astronomical Society | volume=365 | issue=2 | pages=585–589 |date=January 2006 | doi=10.1111/j.1365-2966.2005.09738.x| doi-access=free |url=https://zenodo.org/record/1040372 | bibcode=2006MNRAS.365..585B | postscript=. |arxiv = astro-ph/0510529 | s2cid=16930049 }}
{{cite simbad | title=gam Equ | access-date=2012-07-27 | postscript=. }}
}}
External links
- [http://www.wolframalpha.com/input/?i=gamma+equulei www.wolframalpha.com/input/?i=gamma+equulei]
- [http://www.alcyone.de/SIT/alpcvn/SIT003258 www.alcyone.de/SIT/alpcvn/SIT003258]
{{stars of Equuleus}}
{{DEFAULTSORT:Gamma Equulei}}
Category:Rapidly oscillating Ap stars